1. Field of Invention
The present invention relates to a reflective mirror manufacturing method, an illumination device and a projector.
2. Description of Related Art
Projectors realize image display by modulating, in accordance with image information using a liquid crystal panel, illumination light emitted from an illumination optical system and projecting the modulated light onto a projection surface such as a screen.
The illumination optical system is disposed with an arc tube including a light-emitting portion and a reflector including a reflective surface that reflects the light from the light-emitting portion of the arc tube in a predetermined direction. It is preferable for the illumination device to be able to use, as effectively as possible, the light from the arc tube.
For this reason, a parabolic reflector including a concave surface configured by a paraboloid of revolution is conventionally used as the reflector (e.g., see JP-A-2000-298213). FIG. 4 is a diagram showing an example of an optical system of a projector using such a parabolic reflector. As shown in FIG. 4, a parabolic reflector 930A is used, and by disposing a light emission center of an arc tube 920A in the focal position of the parabolic reflector 930A, the light emitted from the arc tube 920A can be made into substantially parallel light. Thus, the light emitted from the arc tube can be used effectively.
An ellipsoidal reflector including a concave surface configured by an ellipsoid of revolution is also used as the reflector (e.g., see JP-A-2002-90883). FIG. 5 is a diagram showing an example of an optical system of a projector using such an ellipsoidal reflector. As shown in FIG. 5, an ellipsoidal reflector 930B is used, and by disposing the light emission center of an arc tube 920B in one focal point (first focal point) of the ellipsoidal reflector 930B, the light emitted from the arc tube 920B can be effectively focused at another focal point (second focal point) of the ellipsoidal reflector 930B. Thus, the light emitted from the arc tube can be used effectively.
FIG. 6 is a diagram showing another example of an optical system of a projector using such an ellipsoidal mirror. As shown in FIG. 6, an ellipsoidal reflector 930C is used, and by disposing the light emission center of an arc tube 920C in one focal point (first focal point) of the ellipsoidal reflector 930C and disposing a parallelizing lens 945 for making parallel the emission light from the ellipsoidal reflector 930C, the light emitted from the arc tube 920C can be made into substantially parallel light. Thus, the light emitted from the arc tube can be used effectively (e.g., see JP-A-2000-347293).
Such reflectors are usually manufactured by press molding. FIG. 7 is a diagram showing a conventional reflector manufacturing method for explanation.
In the conventional reflector manufacturing method, as shown in FIG. 7, a reflector 930D is molded using a form block 930M disposed with a lower mold 931 including a concave cavity, a press mold 932 disposed so as to surround the periphery of the cavity of the lower mold 931, and a core 933 that slides the inside of a slide-use opening of the press mold 932 towards the inside of the cavity of the lower mold 931. Namely, a softened glass material is supplied to the inside of the cavity of the lower mold 931, the glass material is pressurized by sliding the core 933, and the glass material spreads and fills the inside of the form block 930M. Thus, reference surfaces 937 and 939 are formed by the press mold 932, and a reflective surface 935 is formed by the core 933.